\begin{code}
module TcUnify (
-- Full-blown subsumption
- tcSubOff, tcSubExp, tcGen, subFunTy, TcHoleType,
+ tcSubOff, tcSubExp, tcGen,
checkSigTyVars, checkSigTyVarsWrt, sigCtxt, findGlobals,
-- Various unifications
unifyTauTy, unifyTauTyList, unifyTauTyLists,
- unifyFunTy, unifyListTy, unifyPArrTy, unifyTupleTy,
unifyKind, unifyKinds, unifyOpenTypeKind, unifyFunKind,
- -- Coercions
- Coercion, ExprCoFn, PatCoFn,
- (<$>), (<.>), mkCoercion,
- idCoercion, isIdCoercion
+ --------------------------------
+ -- Holes
+ Expected(..), newHole, readExpectedType,
+ zapExpectedType, zapExpectedTo, zapExpectedBranches,
+ subFunTys, unifyFunTy,
+ zapToListTy, unifyListTy,
+ zapToPArrTy, unifyPArrTy,
+ zapToTupleTy, unifyTupleTy
) where
import HsSyn ( HsExpr(..) )
-import TcHsSyn ( TypecheckedHsExpr, TcPat, mkHsLet )
+import TcHsSyn ( mkHsLet,
+ ExprCoFn, idCoercion, isIdCoercion, mkCoercion, (<.>), (<$>) )
import TypeRep ( Type(..), SourceType(..), TyNote(..), openKindCon )
import TcRnMonad -- TcType, amongst others
import TcType ( TcKind, TcType, TcSigmaType, TcRhoType, TcTyVar, TcTauType,
TcTyVarSet, TcThetaType, TyVarDetails(SigTv),
- isTauTy, isSigmaTy,
+ isTauTy, isSigmaTy, mkFunTys,
tcSplitAppTy_maybe, tcSplitTyConApp_maybe,
tcGetTyVar_maybe, tcGetTyVar,
- mkTyConApp, mkFunTy, tyVarsOfType, mkPhiTy,
+ mkFunTy, tyVarsOfType, mkPhiTy,
typeKind, tcSplitFunTy_maybe, mkForAllTys,
- isHoleTyVar, isSkolemTyVar, isUserTyVar,
+ isSkolemTyVar, isUserTyVar,
tidyOpenType, tidyOpenTypes, tidyOpenTyVar, tidyOpenTyVars,
eqKind, openTypeKind, liftedTypeKind, isTypeKind, mkArrowKind,
hasMoreBoxityInfo, allDistinctTyVars
)
-import qualified Type ( getTyVar_maybe )
import Inst ( newDicts, instToId, tcInstCall )
-import TcMType ( getTcTyVar, putTcTyVar, tcInstType, readHoleResult, newKindVar,
- newTyVarTy, newTyVarTys, newOpenTypeKind, newHoleTyVarTy,
- zonkTcType, zonkTcTyVars, zonkTcTyVarsAndFV, zonkTcTyVar )
+import TcMType ( getTcTyVar, putTcTyVar, tcInstType, newKindVar,
+ newTyVarTy, newTyVarTys, newOpenTypeKind,
+ zonkTcType, zonkTcTyVars, zonkTcTyVarsAndFV )
import TcSimplify ( tcSimplifyCheck )
import TysWiredIn ( listTyCon, parrTyCon, mkListTy, mkPArrTy, mkTupleTy )
-import TcEnv ( TcTyThing(..), tcGetGlobalTyVars, findGlobals )
+import TcEnv ( tcGetGlobalTyVars, findGlobals )
import TyCon ( tyConArity, isTupleTyCon, tupleTyConBoxity )
import PprType ( pprType )
-import Id ( Id, mkSysLocal, idType )
+import Id ( Id, mkSysLocal )
import Var ( Var, varName, tyVarKind )
import VarSet ( emptyVarSet, unitVarSet, unionVarSet, elemVarSet, varSetElems )
import VarEnv
-import Name ( isSystemName, getSrcLoc )
+import Name ( isSystemName )
import ErrUtils ( Message )
import BasicTypes ( Boxity, Arity, isBoxed )
-import Util ( equalLength, notNull )
-import Maybe ( isNothing )
+import Util ( equalLength, lengthExceeds, notNull )
import Outputable
\end{code}
%************************************************************************
%* *
+\subsection{'hole' type variables}
+%* *
+%************************************************************************
+
+\begin{code}
+data Expected ty = Infer (TcRef ty) -- The hole to fill in for type inference
+ | Check ty -- The type to check during type checking
+
+newHole :: TcM (TcRef ty)
+newHole = newMutVar (error "Empty hole in typechecker")
+
+readExpectedType :: Expected ty -> TcM ty
+readExpectedType (Infer hole) = readMutVar hole
+readExpectedType (Check ty) = returnM ty
+
+zapExpectedType :: Expected TcType -> TcM TcTauType
+-- In the inference case, ensure we have a monotype
+zapExpectedType (Infer hole)
+ = do { ty <- newTyVarTy openTypeKind ;
+ writeMutVar hole ty ;
+ return ty }
+
+zapExpectedType (Check ty) = return ty
+
+zapExpectedTo :: Expected TcType -> TcTauType -> TcM ()
+zapExpectedTo (Infer hole) ty2 = writeMutVar hole ty2
+zapExpectedTo (Check ty1) ty2 = unifyTauTy ty1 ty2
+
+zapExpectedBranches :: [a] -> Expected TcType -> TcM (Expected TcType)
+-- Zap the expected type to a monotype if there is more than one branch
+zapExpectedBranches branches exp_ty
+ | lengthExceeds branches 1 = zapExpectedType exp_ty `thenM` \ exp_ty' ->
+ return (Check exp_ty')
+ | otherwise = returnM exp_ty
+
+instance Outputable ty => Outputable (Expected ty) where
+ ppr (Check ty) = ptext SLIT("Expected type") <+> ppr ty
+ ppr (Infer hole) = ptext SLIT("Inferring type")
+\end{code}
+
+
+%************************************************************************
+%* *
+\subsection[Unify-fun]{@unifyFunTy@}
+%* *
+%************************************************************************
+
+@subFunTy@ and @unifyFunTy@ is used to avoid the fruitless
+creation of type variables.
+
+* subFunTy is used when we might be faced with a "hole" type variable,
+ in which case we should create two new holes.
+
+* unifyFunTy is used when we expect to encounter only "ordinary"
+ type variables, so we should create new ordinary type variables
+
+\begin{code}
+subFunTys :: [pat]
+ -> Expected TcRhoType -- Fail if ty isn't a function type
+ -> ([(pat, Expected TcRhoType)] -> Expected TcRhoType -> TcM a)
+ -> TcM a
+
+subFunTys pats (Infer hole) thing_inside
+ = -- This is the interesting case
+ mapM new_pat_hole pats `thenM` \ pats_w_holes ->
+ newHole `thenM` \ res_hole ->
+
+ -- Do the business
+ thing_inside pats_w_holes (Infer res_hole) `thenM` \ answer ->
+
+ -- Extract the answers
+ mapM read_pat_hole pats_w_holes `thenM` \ arg_tys ->
+ readMutVar res_hole `thenM` \ res_ty ->
+
+ -- Write the answer into the incoming hole
+ writeMutVar hole (mkFunTys arg_tys res_ty) `thenM_`
+
+ -- And return the answer
+ returnM answer
+ where
+ new_pat_hole pat = newHole `thenM` \ hole -> return (pat, Infer hole)
+ read_pat_hole (pat, Infer hole) = readMutVar hole
+
+subFunTys pats (Check ty) thing_inside
+ = go pats ty `thenM` \ (pats_w_tys, res_ty) ->
+ thing_inside pats_w_tys res_ty
+ where
+ go [] ty = return ([], Check ty)
+ go (pat:pats) ty = unifyFunTy ty `thenM` \ (arg,res) ->
+ go pats res `thenM` \ (pats_w_tys, final_res) ->
+ return ((pat, Check arg) : pats_w_tys, final_res)
+
+unifyFunTy :: TcRhoType -- Fail if ty isn't a function type
+ -> TcM (TcType, TcType) -- otherwise return arg and result types
+
+unifyFunTy ty@(TyVarTy tyvar)
+ = getTcTyVar tyvar `thenM` \ maybe_ty ->
+ case maybe_ty of
+ Just ty' -> unifyFunTy ty'
+ Nothing -> unify_fun_ty_help ty
+
+unifyFunTy ty
+ = case tcSplitFunTy_maybe ty of
+ Just arg_and_res -> returnM arg_and_res
+ Nothing -> unify_fun_ty_help ty
+
+unify_fun_ty_help ty -- Special cases failed, so revert to ordinary unification
+ = newTyVarTy openTypeKind `thenM` \ arg ->
+ newTyVarTy openTypeKind `thenM` \ res ->
+ unifyTauTy ty (mkFunTy arg res) `thenM_`
+ returnM (arg,res)
+\end{code}
+
+\begin{code}
+zapToListTy :: Expected TcType -- expected list type
+ -> TcM TcType -- list element type
+
+zapToListTy (Check ty) = unifyListTy ty
+zapToListTy (Infer hole) = do { elt_ty <- newTyVarTy liftedTypeKind ;
+ writeMutVar hole (mkListTy elt_ty) ;
+ return elt_ty }
+
+unifyListTy :: TcType -> TcM TcType
+unifyListTy ty@(TyVarTy tyvar)
+ = getTcTyVar tyvar `thenM` \ maybe_ty ->
+ case maybe_ty of
+ Just ty' -> unifyListTy ty'
+ other -> unify_list_ty_help ty
+
+unifyListTy ty
+ = case tcSplitTyConApp_maybe ty of
+ Just (tycon, [arg_ty]) | tycon == listTyCon -> returnM arg_ty
+ other -> unify_list_ty_help ty
+
+unify_list_ty_help ty -- Revert to ordinary unification
+ = newTyVarTy liftedTypeKind `thenM` \ elt_ty ->
+ unifyTauTy ty (mkListTy elt_ty) `thenM_`
+ returnM elt_ty
+
+-- variant for parallel arrays
+--
+zapToPArrTy :: Expected TcType -- Expected list type
+ -> TcM TcType -- List element type
+
+zapToPArrTy (Check ty) = unifyPArrTy ty
+zapToPArrTy (Infer hole) = do { elt_ty <- newTyVarTy liftedTypeKind ;
+ writeMutVar hole (mkPArrTy elt_ty) ;
+ return elt_ty }
+
+unifyPArrTy :: TcType -> TcM TcType
+
+unifyPArrTy ty@(TyVarTy tyvar)
+ = getTcTyVar tyvar `thenM` \ maybe_ty ->
+ case maybe_ty of
+ Just ty' -> unifyPArrTy ty'
+ _ -> unify_parr_ty_help ty
+unifyPArrTy ty
+ = case tcSplitTyConApp_maybe ty of
+ Just (tycon, [arg_ty]) | tycon == parrTyCon -> returnM arg_ty
+ _ -> unify_parr_ty_help ty
+
+unify_parr_ty_help ty -- Revert to ordinary unification
+ = newTyVarTy liftedTypeKind `thenM` \ elt_ty ->
+ unifyTauTy ty (mkPArrTy elt_ty) `thenM_`
+ returnM elt_ty
+\end{code}
+
+\begin{code}
+zapToTupleTy :: Boxity -> Arity -> Expected TcType -> TcM [TcType]
+zapToTupleTy boxity arity (Check ty) = unifyTupleTy boxity arity ty
+zapToTupleTy boxity arity (Infer hole) = do { (tup_ty, arg_tys) <- new_tuple_ty boxity arity ;
+ writeMutVar hole tup_ty ;
+ return arg_tys }
+
+unifyTupleTy boxity arity ty@(TyVarTy tyvar)
+ = getTcTyVar tyvar `thenM` \ maybe_ty ->
+ case maybe_ty of
+ Just ty' -> unifyTupleTy boxity arity ty'
+ other -> unify_tuple_ty_help boxity arity ty
+
+unifyTupleTy boxity arity ty
+ = case tcSplitTyConApp_maybe ty of
+ Just (tycon, arg_tys)
+ | isTupleTyCon tycon
+ && tyConArity tycon == arity
+ && tupleTyConBoxity tycon == boxity
+ -> returnM arg_tys
+ other -> unify_tuple_ty_help boxity arity ty
+
+unify_tuple_ty_help boxity arity ty
+ = new_tuple_ty boxity arity `thenM` \ (tup_ty, arg_tys) ->
+ unifyTauTy ty tup_ty `thenM_`
+ returnM arg_tys
+
+new_tuple_ty boxity arity
+ = newTyVarTys arity kind `thenM` \ arg_tys ->
+ return (mkTupleTy boxity arity arg_tys, arg_tys)
+ where
+ kind | isBoxed boxity = liftedTypeKind
+ | otherwise = openTypeKind
+\end{code}
+
+
+%************************************************************************
+%* *
\subsection{Subsumption}
%* *
%************************************************************************
expected_ty.
\begin{code}
-type TcHoleType = TcSigmaType -- Either a TcSigmaType,
- -- or else a hole
-
-tcSubExp :: TcHoleType -> TcSigmaType -> TcM ExprCoFn
-tcSubOff :: TcSigmaType -> TcHoleType -> TcM ExprCoFn
-tcSub :: TcSigmaType -> TcSigmaType -> TcM ExprCoFn
+tcSubExp :: Expected TcRhoType -> TcRhoType -> TcM ExprCoFn
+tcSubOff :: TcSigmaType -> Expected TcSigmaType -> TcM ExprCoFn
\end{code}
These two check for holes
\begin{code}
tcSubExp expected_ty offered_ty
- = checkHole expected_ty offered_ty tcSub
+ = traceTc (text "tcSubExp" <+> (ppr expected_ty $$ ppr offered_ty)) `thenM_`
+ checkHole expected_ty offered_ty tcSub
tcSubOff expected_ty offered_ty
= checkHole offered_ty expected_ty (\ off exp -> tcSub exp off)
-- Otherwise it calls thing_inside, passing the two args, looking
-- through any instantiated hole
-checkHole (TyVarTy tv) other_ty thing_inside
- | isHoleTyVar tv
- = getTcTyVar tv `thenM` \ maybe_ty ->
- case maybe_ty of
- Just ty -> thing_inside ty other_ty
- Nothing -> putTcTyVar tv other_ty `thenM_`
- returnM idCoercion
+checkHole (Infer hole) other_ty thing_inside
+ = do { writeMutVar hole other_ty; return idCoercion }
-checkHole ty other_ty thing_inside
+checkHole (Check ty) other_ty thing_inside
= thing_inside ty other_ty
\end{code}
No holes expected now. Add some error-check context info.
\begin{code}
+tcSub :: TcSigmaType -> TcSigmaType -> TcM ExprCoFn -- Locally used only
tcSub expected_ty actual_ty
= traceTc (text "tcSub" <+> details) `thenM_`
addErrCtxtM (unifyCtxt "type" expected_ty actual_ty)
- (tc_sub expected_ty expected_ty actual_ty actual_ty)
+ (tc_sub expected_ty expected_ty actual_ty actual_ty)
where
details = vcat [text "Expected:" <+> ppr expected_ty,
text "Actual: " <+> ppr actual_ty]
| isSigmaTy actual_ty
= tcInstCall Rank2Origin actual_ty `thenM` \ (inst_fn, body_ty) ->
tc_sub exp_sty expected_ty body_ty body_ty `thenM` \ co_fn ->
- returnM (co_fn <.> mkCoercion inst_fn)
+ returnM (co_fn <.> inst_fn)
-----------------------------------
-- Function case
-- when the arg/res is not a tau-type?
-- NO! e.g. f :: ((forall a. a->a) -> Int) -> Int
-- then x = (f,f)
--- is perfectly fine!
+-- is perfectly fine, because we can instantiat f's type to a monotype
+--
+-- However, we get can get jolly unhelpful error messages.
+-- e.g. foo = id runST
+--
+-- Inferred type is less polymorphic than expected
+-- Quantified type variable `s' escapes
+-- Expected type: ST s a -> t
+-- Inferred type: (forall s1. ST s1 a) -> a
+-- In the first argument of `id', namely `runST'
+-- In a right-hand side of function `foo': id runST
+--
+-- I'm not quite sure what to do about this!
tc_sub exp_sty exp_ty@(FunTy exp_arg exp_res) _ (TyVarTy tv)
- = ASSERT( not (isHoleTyVar tv) )
- getTcTyVar tv `thenM` \ maybe_ty ->
+ = getTcTyVar tv `thenM` \ maybe_ty ->
case maybe_ty of
Just ty -> tc_sub exp_sty exp_ty ty ty
Nothing -> imitateFun tv exp_sty `thenM` \ (act_arg, act_res) ->
tcSub_fun exp_arg exp_res act_arg act_res
tc_sub _ (TyVarTy tv) act_sty act_ty@(FunTy act_arg act_res)
- = ASSERT( not (isHoleTyVar tv) )
- getTcTyVar tv `thenM` \ maybe_ty ->
+ = getTcTyVar tv `thenM` \ maybe_ty ->
case maybe_ty of
Just ty -> tc_sub ty ty act_sty act_ty
Nothing -> imitateFun tv act_sty `thenM` \ (exp_arg, exp_res) ->
imitateFun :: TcTyVar -> TcType -> TcM (TcType, TcType)
imitateFun tv ty
- = ASSERT( not (isHoleTyVar tv) )
- -- NB: tv is an *ordinary* tyvar and so are the new ones
+ = -- NB: tv is an *ordinary* tyvar and so are the new ones
-- Check that tv isn't a type-signature type variable
-- (This would be found later in checkSigTyVars, but
%************************************************************************
%* *
-\subsection{Coercion functions}
-%* *
-%************************************************************************
-
-\begin{code}
-type Coercion a = Maybe (a -> a)
- -- Nothing => identity fn
-
-type ExprCoFn = Coercion TypecheckedHsExpr
-type PatCoFn = Coercion TcPat
-
-(<.>) :: Coercion a -> Coercion a -> Coercion a -- Composition
-Nothing <.> Nothing = Nothing
-Nothing <.> Just f = Just f
-Just f <.> Nothing = Just f
-Just f1 <.> Just f2 = Just (f1 . f2)
-
-(<$>) :: Coercion a -> a -> a
-Just f <$> e = f e
-Nothing <$> e = e
-
-mkCoercion :: (a -> a) -> Coercion a
-mkCoercion f = Just f
-
-idCoercion :: Coercion a
-idCoercion = Nothing
-
-isIdCoercion :: Coercion a -> Bool
-isIdCoercion = isNothing
-\end{code}
-
-%************************************************************************
-%* *
\subsection[Unify-exported]{Exported unification functions}
%* *
%************************************************************************
%************************************************************************
%* *
-\subsection[Unify-fun]{@unifyFunTy@}
-%* *
-%************************************************************************
-
-@subFunTy@ and @unifyFunTy@ is used to avoid the fruitless
-creation of type variables.
-
-* subFunTy is used when we might be faced with a "hole" type variable,
- in which case we should create two new holes.
-
-* unifyFunTy is used when we expect to encounter only "ordinary"
- type variables, so we should create new ordinary type variables
-
-\begin{code}
-subFunTy :: TcHoleType -- Fail if ty isn't a function type
- -- If it's a hole, make two holes, feed them to...
- -> (TcHoleType -> TcHoleType -> TcM a) -- the thing inside
- -> TcM a -- and bind the function type to the hole
-
-subFunTy ty@(TyVarTy tyvar) thing_inside
- | isHoleTyVar tyvar
- = -- This is the interesting case
- getTcTyVar tyvar `thenM` \ maybe_ty ->
- case maybe_ty of {
- Just ty' -> subFunTy ty' thing_inside ;
- Nothing ->
-
- newHoleTyVarTy `thenM` \ arg_ty ->
- newHoleTyVarTy `thenM` \ res_ty ->
-
- -- Do the business
- thing_inside arg_ty res_ty `thenM` \ answer ->
-
- -- Extract the answers
- readHoleResult arg_ty `thenM` \ arg_ty' ->
- readHoleResult res_ty `thenM` \ res_ty' ->
-
- -- Write the answer into the incoming hole
- putTcTyVar tyvar (mkFunTy arg_ty' res_ty') `thenM_`
-
- -- And return the answer
- returnM answer }
-
-subFunTy ty thing_inside
- = unifyFunTy ty `thenM` \ (arg,res) ->
- thing_inside arg res
-
-
-unifyFunTy :: TcRhoType -- Fail if ty isn't a function type
- -> TcM (TcType, TcType) -- otherwise return arg and result types
-
-unifyFunTy ty@(TyVarTy tyvar)
- = ASSERT( not (isHoleTyVar tyvar) )
- getTcTyVar tyvar `thenM` \ maybe_ty ->
- case maybe_ty of
- Just ty' -> unifyFunTy ty'
- Nothing -> unify_fun_ty_help ty
-
-unifyFunTy ty
- = case tcSplitFunTy_maybe ty of
- Just arg_and_res -> returnM arg_and_res
- Nothing -> unify_fun_ty_help ty
-
-unify_fun_ty_help ty -- Special cases failed, so revert to ordinary unification
- = newTyVarTy openTypeKind `thenM` \ arg ->
- newTyVarTy openTypeKind `thenM` \ res ->
- unifyTauTy ty (mkFunTy arg res) `thenM_`
- returnM (arg,res)
-\end{code}
-
-\begin{code}
-unifyListTy :: TcType -- expected list type
- -> TcM TcType -- list element type
-
-unifyListTy ty@(TyVarTy tyvar)
- = getTcTyVar tyvar `thenM` \ maybe_ty ->
- case maybe_ty of
- Just ty' -> unifyListTy ty'
- other -> unify_list_ty_help ty
-
-unifyListTy ty
- = case tcSplitTyConApp_maybe ty of
- Just (tycon, [arg_ty]) | tycon == listTyCon -> returnM arg_ty
- other -> unify_list_ty_help ty
-
-unify_list_ty_help ty -- Revert to ordinary unification
- = newTyVarTy liftedTypeKind `thenM` \ elt_ty ->
- unifyTauTy ty (mkListTy elt_ty) `thenM_`
- returnM elt_ty
-
--- variant for parallel arrays
---
-unifyPArrTy :: TcType -- expected list type
- -> TcM TcType -- list element type
-
-unifyPArrTy ty@(TyVarTy tyvar)
- = getTcTyVar tyvar `thenM` \ maybe_ty ->
- case maybe_ty of
- Just ty' -> unifyPArrTy ty'
- _ -> unify_parr_ty_help ty
-unifyPArrTy ty
- = case tcSplitTyConApp_maybe ty of
- Just (tycon, [arg_ty]) | tycon == parrTyCon -> returnM arg_ty
- _ -> unify_parr_ty_help ty
-
-unify_parr_ty_help ty -- Revert to ordinary unification
- = newTyVarTy liftedTypeKind `thenM` \ elt_ty ->
- unifyTauTy ty (mkPArrTy elt_ty) `thenM_`
- returnM elt_ty
-\end{code}
-
-\begin{code}
-unifyTupleTy :: Boxity -> Arity -> TcType -> TcM [TcType]
-unifyTupleTy boxity arity ty@(TyVarTy tyvar)
- = getTcTyVar tyvar `thenM` \ maybe_ty ->
- case maybe_ty of
- Just ty' -> unifyTupleTy boxity arity ty'
- other -> unify_tuple_ty_help boxity arity ty
-
-unifyTupleTy boxity arity ty
- = case tcSplitTyConApp_maybe ty of
- Just (tycon, arg_tys)
- | isTupleTyCon tycon
- && tyConArity tycon == arity
- && tupleTyConBoxity tycon == boxity
- -> returnM arg_tys
- other -> unify_tuple_ty_help boxity arity ty
-
-unify_tuple_ty_help boxity arity ty
- = newTyVarTys arity kind `thenM` \ arg_tys ->
- unifyTauTy ty (mkTupleTy boxity arity arg_tys) `thenM_`
- returnM arg_tys
- where
- kind | isBoxed boxity = liftedTypeKind
- | otherwise = openTypeKind
-\end{code}
-
-
-%************************************************************************
-%* *
\subsection{Kind unification}
%* *
%************************************************************************
projects / ghc-hetmet.git / blobdiff